Unit 5: Heredity

Question 1

meiosis

Answer 1

process of cell division used in gamete formation; forms haploid (n) gametes from diploid (2n) parent cells, helping to maintain the proper number of chromosomes in the offspring

Question 2

meiosis 1

Answer 2

consists of four stages: prophase I, metaphase I, anaphase I, and telophase I

Question 3

prophase I

Answer 3

nuclear membrane breaks down and chromosomes condense and become visible; homologous chromosomes pair up and genetic recombination (crossing over) can occur

Question 4

metaphase I

Answer 4

chromosomes line up in homologous pairs in the middle of the cell

Question 5

anaphase I

Answer 5

pairs of homologous chromosomes separate (are pulled apart), number of chromosomes stays the same

Question 6

telophase I & cytokinesis

Answer 6

two new nuclei are formed

Question 7

meiosis II

Answer 7

consists of four stages: prophase II, metaphase II, anaphase II, and telophase II; is not preceded by DNA replication

Question 8

prophase II

Answer 8

chromosomes again condense and become visible

Question 9

metaphase II

Answer 9

chromosomes line up in a single line along the middle of the cell

Question 10

anaphase II

Answer 10

sister chromatids separate and move to opposite ends of the cell; each sister chromatid will have its own centromere once this separation has occurred, making them chromosomes

Question 11

telophase II

Answer 11

each of the two cells are split in half, resulting in four cells

Question 12

how does meiosis generate genetic diversity?

Answer 12

1) in prophase I, homologous chromosomes pair up in synapsis to form tetrads, which allows them to cross over and exchange genetic info
2) in metaphase I, each pair of chromosomes lines up and assorts independently, with different parents having the paternal chromosomes on one side and the maternal chromosome on the other side

Question 13

genes that are farther apart will have a ________ recombination frequency

Answer 13

higher

Question 14

genes that are closer to each other will have a ______ recombination frequency

Answer 14

lower

Question 15

linked genes

Answer 15

genes that are close together on the same chromosome tend to be inherited together more often, because their recombination frequency is lower

Question 16

mendel’s law of segregation

Answer 16

an organism carries two variations of every trait (alleles), one from each parent, and these alleles segregate (separate) independently into gametes; this segregation occurs during anaphase I of meiosis when chromosomes are separated into separate gametes

Question 17

mendel’s law of independent assortment

Answer 17

genes for different traits segregate independently one another; this independent assortment occurs during metaphase I of meiosis

Question 18

genotype

Answer 18

genetic makeup or alleles for the trait in an organism

Question 19

phenotype

Answer 19

physical expression of the genotype

Question 20

homozygous

Answer 20

having two copies of the same allele for a trait (aa, AA)

Question 21

heterozygous

Answer 21

having two different alleles for a trait (Aa)

Question 22

dominant

Answer 22

requires only one copy of the allele for the trait to be expressed in the phenotype

Question 23

recessive

Answer 23

requires two copies of the allele for the trait

Question 24

monohybrid cross

Answer 24

cross where both parents are heterozygous for the trait

Question 25

dihybrid cross

Answer 25

two organisms heterozygous for the same two traits are crossed

Question 26

test cross

Answer 26

cross between an organism with a dominant phenotype and an organism with the recessive phenotype

Question 27

autosomes

Answer 27

where most genes are located; chromosomes not directly involved in sex determination; males and females are equally likely to inherit genes on autosomes

Question 28

sex chromosomes

Answer 28

involved in sex determination; genes on sex chromosomes have different inheritance patterns than those on autosomes; nonhomologous: females have two X chromosomes, while males have one X and one Y chromosomes

Question 29

sex-linked genes

Answer 29

genes located on sex chromosomes

Question 30

traits that are coded for by sex-linked recessive alleles are more likely to be expressed in ______ because they ________

Answer 30

males; only have one X chromosome

Question 31

multiple gene inheritance

Answer 31

some traits are produced by multiple genes acting together to produce the phenotype; because more than one gene is involved in producing the trait, mendelian ratios do no tapply

Question 32

nonnuclear inheritance

Answer 32

mitochondria and chloroplasts have their own DNA separate from nuclear DNA; this DNA does not follow the inheritance patterns found in nuclear DNA; these traits demonstrate maternal inheritance because the ovules are larger than the sperm, making them contribute more mitochondria and mtDNA than the sperm; the trait can be passed to either child from the mother but males do not pass the trait on

Question 33

phenotypic plasticity

Answer 33

the ability of the same genotypes to produce different phenotypes in response to different environmental factors; the environment can affect gene expression and the resulting phenotype of an organism